Process of producing ammonium sulphate



July 11, 1933.

50/,0/7 a fe To Sforaye c. G. ATWATER 1,917,915 PROCESS OF PRODUCING AmaoNIUM SULPHATE Filed Ju1y 7, 1930 Gas In lef Safurafor Low 2 Add +2 3 5 4 .Safum for H/y/l 5 fic/d 8 Gas 00/167" INVENTOR Ana mb 9. m

ATTQEQNEYS Patented July 11, 1933 cnnrs'rorrzna e. A'rwA'rER, or raaavrowu, new vonunssrsuoa To 'rnunAnnsrrf COMPANY, or New roux, n. Y., a conroen'rrou or new JERSEY- PROCESS or riaonnorue anmmmr mm I Application filed July 7, 1930. SerialNo. 466,125.

This invention relates to the production ammonium sulphate from coke oven or sim1- lar gases, and has for its object the provision of an improved method facilitating theepros duction of largercrystals of sulphate, better in quality and less liable to absorb moisture and become caked.

According to the practice generally employed, ammonium sulphate is produced from coke oven and similar gases by passing the gases through a saturatorcontaining sulphuric acid. A. low strength of acid is conducive to the formation of largecrvstals of sulphate, which aremore desirable than those of small size;

Vitha low strength acid, however, an appreciable part of the ammonia contained in the gases is lost, because the acid is not capable of extracting all of it in the limited time of passage. a low strength acid ensures the production of crystals of large size, it nevertheless has the disadvantage of resulting in an appreciable loss of ammonia. It also renders a'ccm'ate control more diliicult as a drop in acid strength of the Weak acid may result in loss of ammonia, Whereas a reduction in strength of the stronger acid is not so detrimental.

It is the purpose of the present invention to overcome, so far as possible, the above mentioned disadvantage and yet not hamper the production of sulphate crystals of desirable size.

Generally speaking, the present invention concerns a method providing for the pas sage of the ammonia containing gases through a. series of saturators containing acid of successively greater concentration, WllOlTfiby the ammonia which is not extracted in one is extracted in another of the saturators. The invention providesfurther for the transfer of the sulphate from succeeding saturators back to the one having an acid bath o1 a strength most conducive for the formation of crystals of large size. 7

For practical purposes, the saturators in the series need not exceed twoin number, provided the acid bath of the second saturator is of sufficient concentration to extract Therefore, although the use of equipped with a suitable valve.

substantially allofthe ammonia passed over from the first saturator.

As'an example of such an'installation, reference is made to the accompanying flow sheet, which, together with the description relating thereto, is intended to serve merely as a typical. illustration of the invention described.

Considering the flow sheet more in detail,

the ammonia-containing gases are supplied through a suitahle pipingsystem 'toa saturator containing acid of low strength, from which they pass into a second saturator, containing acid of highen-strength before being discharged to the gas holder.

Apiping arrangement which maybe used satisfactorily is represented in'the drawing, wherein each saturator is shown as being provided with an inlet pipe connected'to the supply and an outlet pipe connected to the gas outlet. An additional pipeconneca ing the outlet of the first saturator to the in let of the second saturator is also provided.

To permit proper control, each pipe is Accordingly, when the saturators are to be operated in series, valves 1,3 and 5 are'opened and valves 2 and 4 closed. If for any reason independent operation 'isto; be efiected, valve 3 in the connecting pipe is closed and the remaining valves opened.

In most instances an acid strength of approximately 2 Will be found suitable for the first saturator While the bath of the second may be made as high as.5-6% or even higher.

The first bath being ofsuitably lOW concontration, the vgases passing therethrough combine With the sulphuric acid to form large crystals of ammonium sulphate, and j then pass into the second saturator, Where the last traces of ammonia are extracted to formsulphatccrystals of small size. The smallcrystals and/or the strong ammonium sulphate solution thus formed in the second saturator are introduced into the first saturator and therein'built up into large crystals, after Which'they may be periodically or continu-- As is to be expected, the transfer of the sulphate from the second saturator to the first results in the addition of a certain amount or" higher strength acid to the bath of the first saturator, but such condition may be utilized'to eliminate the necessity for periodically adding fresh acid to the first saturator. In fact, the entire amount of fresh acid, Which it may be found necessary to add to thesaturators to keep 'them'at the desired concenration, may all be added to the second saturator, and the transfer of sulphate so regulated as to ensure the passage of the required amount of higher strength acid to the first saturator to keep it at proper strength. 7

It is fully realized that as a suitable operating unit two interconnected saturators have been proposed before, but so far as is known,

the acid strength has been the'same in each and the two saturators have been used only to p e unit the cutting out of one for repair Without interfering with the operation of the plant. Seriesope-ration of two or more saturators in the manner of the present method .has heretofore never been practiced.

However, by properly rearranging the piping, which would have to be Worked out in accordance with the conditions existing in each plant, a unit of two saturators intended for alternate operation can be connected up to opera'te'in series-in accordance with the present invention. This may require increasing the delivery pressure of the exhauster a Iclaim: v

1. A method o1 producing large crystals of ammonium sulphate from LII1II1OI1llC011-- taming gases, which comprises passlng the gases successively through a series of saturators each containing sulphuric acid of different strength, the acid in the first of said saturators being of a strength conducive to the formation of large crystals of sulphate,

forming crystals of smaller size in a sucing gases successively through a series of saturator-s, each containing sulphuric acid of different strength, the acid in the first of said saturators being of a strength conducive to the formation of large crystals of sulphate, continuously forming crystals of smaller size in a succeeding saturator, returning the sulphate crystals for-med in said succeeding saturator to said first saturator, retaining said returned sulphate crystals in said first saturator until the crystal size thereof is substantially larger thanthat of the sulphate crystals from said succeeding saturator and continuously removing large crystals of sulphate from said first saturator.

' CHRISTOPHER c. ATWATER 

